Two of the comments questioned that statement, and so I thought I would explain, or try to.

The easy answer is that being around success you learn how people create their “luck”:

When you have a friend who gets a story published, you learn about markets, and niches, and submission processes.

When you know writers with agents, you hear how they made that happen. You take a look at a query letter that worked, and you learn. You hear stories about rejection, and you take heart. And perhaps you have opportunities to meet agents in the process.